Vertical binocular misalignment (VBM) can degrade image quality and contribute to visual discomfort in stereoscopic head-mounted displays, particularly for see-through AR. In this project, we investigate whether VBM impairs visual performance — namely, users’ ability to process briefly-presented AR content, like text notifications. We also quantify how the impacts of VBM vary with an AR system’s virtual image distance (VID). Across three experiments, participants were asked to (a) detect and (b) resolve, fuse and process AR content presented with constant and time-varying VBM. Short text stimuli (words or sentences) were briefly presented on a multi-display haploscope, using additive and transmissive displays to emulate see-through AR. Experiments were repeated at three VIDs: 57, 100, 139 cm (1.75, 1, 0.72 D). The magnitude and frequency of VBM was adaptively sampled on each trial. Visual performance (as measured by participants’ time to fuse and read text) was steadily impaired with increasing VBM. For high VBM magnitudes, time to fuse did not meaningfully differ between VIDs; for low VBM, time to fuse was fastest in the furthest VID. Participants’ ability to detect VBM also improved at further VIDs. Correlations were observed between all three user outcome measures: detection, visual performance, and comfort. Overall, we find that visual performance metrics provide a useful framework to complement detection and visual comfort approaches, consistent with recent work on VBM and related artifacts in AR. The results of this study can be used to inform VBM tolerance guidelines and VID placement tradeoffs in future AR devices.

Visual-vestibular conflicts (VVCs) are a primary contributor to visually induced motion sickness (VIMS) in head-mounted displays

A key feature of augmented reality (AR) is the ability to display virtual content that appears stationary as users move throughout the physical world (‘world-locked rendering’). Imperfect world-locked rendering gives rise to perceptual artifacts that can negatively impact user experience. One example is random variation in the position of virtual objects that are intended to be stationary (jitter’). The human visual system is highly attuned to detect moving objects, and moreover it can disambiguate between the retinal velocities that arise from object motion and self-motion, respectively. In this study, we investigated how the perceptibility of AR object jitter varies as a function of user self-motion. Using a commercially available AR HMD to display a 3D textured cube, we measured sensitivity to added jitter versus a no-jitter reference using a two-interval forced choice task. Three user motion conditions (stationary, head rotation, and walking) and three object placement conditions (floating in free space, on a desk, and against a wall) were tested in a full factorial design. We hypothesized that (1) as users move their head and eyes during self-motion, their sensitivity to jitter will decrease, due to added retinal velocity; and (2) rendering virtual objects near physical surfaces will increase sensitivity to jitter, by providing proximal veridical visual cues. Psychometric thresholds indicated that users were significantly less sensitive to jitter during self-motion than when they were stationary, consistent with hypothesis (1). Users were also more sensitive to jitter in one of the two object placement conditions, providing partial support for hypothesis (2). To generalize beyond distinct user motion and object placement conditions, we also analyzed eye tracking data. The amount of retinal slip (i.e. how much gaze drifted across the virtual object) predicted jitter thresholds better than recorded head movements alone, suggesting a retinally-driven decrease in jitter sensitivity during self-motion. These results can be used to inform requirements for AR world-locked rendering systems, as well as how these may be updated dynamically using online measurement of user head and eye movements.

When using a see-through augmented reality head-mounted display system (AR HMD), a user’s perception of virtual content may be degraded by a variety of perceptual artifacts resulting from the architecture of rendering and display pipelines. In particular, virtual content that is rendered to appear stationary in the real world (worldlocked) can be susceptible to spatial and temporal 3D position errors. A subset of these errors, termed jitter, result from mismatches between the spatial localization, rendering, and display pipelines, and can manifest as perceived motion of intended-to-be stationary content. Here, we employ psychophysical methods to quantify the perceptibility of jitter artifacts in an AR HMD. For some viewing conditions, participants perceived jitter that was smaller than the pixel pitch of the testbed (i.e., subpixel jitter). In general, we found that jitter perceptibility increased as viewing distance increased and decreased as background luminance increased. We did not find that the contrast ratio of virtual content, age, or experience with AR/VR modulatedjitter perceptibility. Taken together, this study quantifies the degree of jitter that a user can perceive in an AR HMD and demonstrates that it is critical to consider the capabilities and limits of the human visual system when designing the next generation of spatial computing platforms.